In general, a vehicle alternator is horizontally mounted to an engine so that a rotation shaft of the alternator is parallel to the ground, that is, horizontal, as shown in FIG. 5.
For example, Unexamined Japanese Patent Publication No. JP-A-2002-315283 discloses a vehicle alternator mounted in the above manner. In this alternator, a rear frame is formed with a discharge port for discharging abrasion powder generated by brushes. Further, it is designed so that the discharge port is open in a downward direction. However, if a mounting position or angle of the alternator is changed with differences of vehicles or engine layout, it is required to newly form or redesign the rear frame so that the discharge port is always open in the downward direction. Accordingly, it takes time to design or plan the rear frame and results in an increase in cost.
In addition, because the space of an engine compartment tends to be narrowed, recently. If the alternator is arranged such that electrical components such as a rectifying device provided on the rear side of the alternator are proximate to heat-generating components such as an exhaust manifold through a small gap between them, the electrical components will be affected by heat. Therefore, durability of the electrical components of the alternator will be decreased.
As another example, unexamined Japanese Patent Publication No. JP-A-2002-119008 proposes to mount a vehicle alternator such that a pulley faces upward and a rear cover faces downward. That is, the electrical components are located closer to the ground. Although the electrical components are covered with a rear cover, the rear cover forms discharge openings for discharging water and air intake openings for sucking air. Therefore, the electrical components covered with the rear cover will be easily affected by splashed water or mud from the ground. As a result, the electrical components will be rusted or electrically corroded. Thus, durability of those components will be largely decreased. Further, in this arrangement, it is difficult to properly discharge the brush powder. If the brush powder will adhere to slip rings on the rotation shaft, the brushes will be abnormally abraded.